West System Colloidal Silica Filler for Epoxy — 2 oz Non-Sag Thickening Additive

West System 406-2 Colloidal Silica is a finely powdered thickening additive that turns WEST SYSTEM epoxy into a creamy, non-sag paste for fairing, filleting, and vertical/overhead applications.

When working with epoxy, controlling flow and body is essential for neat, durable results. The 406-2 Colloidal Silica filler from West System is formulated to thicken epoxy resin and hardener blends, creating a stable, off-white paste that resists runoff and improves handling. Made in the USA and specifically compatible with WEST SYSTEM epoxy systems, this additive lets you tailor viscosity for tasks that require a heavier-bodied mix without changing cure characteristics.

How does West System 406-2 stop epoxy from running on vertical or overhead surfaces?

Adding a small measured amount of 406 colloidal silica increases the mixture’s internal structure, producing a non-sag paste that clings to surfaces. This makes it easier to apply fairing or fill coats on vertical hulls, keels, or overhead areas without drips.

• Creates a paste-like consistency that holds on vertical surfaces.
• Reduces sag and runoff for cleaner placement.
• Works with both resin and hardener blends for consistent handling.

What thickness and appearance can I expect after mixing 406-2 with WEST SYSTEM epoxy?

When mixed in appropriate proportions, 406 colloidal silica produces a creamy, off-white paste that stays workable for shaping and fairing. The additive increases body without significantly altering cure time or final strength when used as directed with WEST SYSTEM epoxy.

• Turns liquid epoxy into a stable, cream-colored paste.
• Maintains structural integrity suited for fairing and filleting.
• Easy to sand and finish once cured to desired hardness.

How much 406-2 should I add and when should I mix it into the epoxy?

Start with small increments and blend until you reach the desired consistency — a little goes a long way. Add the powder after fully mixing the resin and hardener so the thickener disperses evenly and you avoid lumps.

• Add gradually and hand-stir thoroughly for uniform texture.
• Mix into fully combined resin/hardener to ensure proper integration.
• Adjust quantity to achieve light paste for fillets or thicker body for fairing.

Will using 406-2 affect the epoxy’s cure or strength?

When used as a viscosity modifier in recommended amounts with WEST SYSTEM epoxy resins and hardeners, 406 colloidal silica customizes handling without fundamentally changing cure characteristics or structural performance. It primarily alters rheology to improve placement and finish work.

• Compatible with WEST SYSTEM epoxy systems for predictable results.
• Designed to modify handling, not to replace structural fillers.
• Use in conjunction with other WEST SYSTEM fillers for specialized strength or bulk needs.

Who this is for: West System 406-2 Colloidal Silica is aimed at boatbuilders, repair technicians, composite fabricators, and DIY enthusiasts who need controlled epoxy body for fairing, filleting, patching, or any application requiring non-sag behavior. It’s especially useful when working on vertical or overhead surfaces, when a creamy, sandable finish matters, or when you need predictable handling with WEST SYSTEM resins and hardeners. If you require bulk structural fill or gap-filling with high compressive strength, consider combining 406-2 with other WEST SYSTEM fillers to achieve the desired mechanical properties.